Grease manufacture



June 8, 1937. c.- o. GREENLEE 2,083,015

GREASE MANUFACTURE Filed June 5, 1935 INVENTOR Charles 0. Weenlea ATTORNEY Patented June 8, 1937 UNITED STATES GREASE MANUFACTURE Charles 0. Greenlee, Casper, Wyo., assignor to Standard Oil Company, Chicago, 111., a corporation of Indiana Application June 5, 1935, Serial No. 25,011

13 Claims.

This invention relates to the manufacture of greases and particularly to the manufacture of calcium soap greases in open kettles.

It is an object of my invention to provide a method for the manufacture of calcium soap greases such as cup greases, pressure gun greases, transmission greases, etc., which will produce a higher quality and more uniform grease than has previously been possible using openkettles.

It is a further object of my invention to provide a method of grease manufacture in which the necessary time for the completion of a batch of grease is greatly reduced. A still further object of my invention is to provide a process whereby a grease free from lumps and having a smooth,

uniform texture may be produced. Another important object of my invention is to provide a method whereby a greater amount of oil and a lesser amount of soap can be used to produce a grease of a given consistency as compared with prior art methods. It-is also an object of my invention to provide a method of grease manu-' 3 The various types of calcium soap greases are by far the commonest and most important types of greases used by modern industry. In general these greases consist of calcium soap, oil and water. although other constituents may be pres-- ent in some cases. The various grades of cup greases may contain from 10% up to or even of calcium soap, from to l of water, together with lubricating oil of the desired viscosity to'make 100%. :1) gun grease is similar to a cup grease but contains in the neighborhood of 10% Transmission greases are again similar but are commonly characterized by a lower soap content, for instance 3% to 6%. In all these cases the optimum water content varies directly with the soap content so that in the casebf transmission greasesthe most desirable water content is somewhat under All of the percentages given are on a weight basis. These various types of calcium soap greases -have in the past' been made in mixers of the open kettle type of from 5 to 15 feet in diameter and of depthsomewhat greater than their diameter. These kettles are usually and preferably heated by means-of steam jackets, but in. some A typical pressure calcium soap.

cases they are heated by direct firing. More recently, closed kettles in which the grease can be subjected to super-atmospheric pressures have been used and it is possible to achieve some of the improvements which characterize my invention by the use of pressure equipment of this type. This equipment is, however, highly expensive and has; other disadvantages. My invention makes it possible to achieve the results characteristic of the use of pressure kettles without their disadvantages by the use of open kettles of the type heretofore used. I

Kettles used in grease manufacture are customarily equipped with internal stirrers of a rotary type. I

Various procedures have been used in the past in making calcium soap greases in open kettles. One of the best of those known to the prior art and one which is used in common practice in the manufacture of cup greases consists of charging the lime, fatty acid and about 10% of the total oil required into an open kettle equipped with an internal mixer and heating to about 235 F. to 250 F., at which temperature neutralization, or as commonly called in the trade, "saponification is completed. According to this prior art method the soap thus formed was then allowed to cool to about the boiling point of water or slightly above the boiling point of water, after which the required amount of water was rapidly added. Before the water could turn to steam and be driven off from the soap, cold oil was added'as rapidly as possible to cool the batch and the grease was thus formed.

In many cases it has been found desirable to use a little caustic soda along with the lime. This appears to speed up the saponiflcation" and to give a somewhat better result. From 1% to 10% of. the required lime may suitably be replaced by caustic soda. -Although' my invention is applicable to greases made from lime without the addition of soda, it is particularly applicable to greases in which some soda. is used.

My improved method of making cup greases, pressure gun greases and transmission greases. while similar to the old up to the point where the saponification has been completed at atemperature of about 215 F. to 250 F. and preferably 230 F. to 250 F., differs radically in procedure from this point on. Furthermore, I prefer to use more oil at the start of the batch than has been characteristic of the prior art. I prefer to add from about 15% to about 30% of the total oil required at the beginning of the batch instead of about 10% as has heretofore been typical; After saponification is completed I discontinue heating the kettle and small streams of oil and water are started in at once. The water stream is regulated by the amount of foaming. The batch will rise a few inches and must not be allowed to foam very much. Cutting down the size of the water stream will reduce the foaming should it be considered to be too great.

The batch is circulated by means of a pump taking suction from the bottom of the kettle and discharging into the top; this circulation is started at the time the oil and water streams are started. As the batch cools down it will go through a characteristic change in condition and appearance at about the boiling point of water. This change in condition turns the batch from a soapy structure to a typical grease and the batch becomes much heavier.

I believe that this change in condition is caused by an inversion of the emulsion. In other words the soapy structure appears to be an oil-in-water emulsion, whereas the final grease should be a water-in-oi emulsion. Some of the advantages of my invention appear to be due to the fact that the grease constituents are kept in constant equilibrium with water during the cooling and up to the point at which this change in condition occurs.

when the cooling has proceeded past the point at which this change in condition ocqurs, the water content of thefinished grease can be considered fixed and the water stream is shut off. The batch is then finished by adding the remainder of the required oil. This oil can be added as rapidly as it can be incorporated in the grease.

By circulating the batch and adding the water and oil in the described method I am able to finish the grease batch in about two-thirds the time required by the old procedure.

Other advantages of my method are:

1. The chance of producing a grease full of lumps is greatly reduced, due to the fact that a larger amount of oil is used at the start and all changes take place at a gradual and uniform rate.

" In the old method in which a large amount of water and oil is dumped in on a heavy soap a large portion of the batches turn out to be lumpy or otherwise unsatisfactory. I J

2. My procedure also gives a smooth grease of uniform texture without graininess. This is especially valuable -in the case of heavy pressure gun greases.

3. I am enabled to use a greater amount of oil in proportion to the soap, which is one of the principal advantages of my method. Oil is much cheaper than soap and it is desired to use as high a proportion of it as possible and yet make the same quality of product.

The preceding descriptionhas had to do principally with the manufacture of greases from ordinary fatty acids such as oleic acid, mixed animal fatty acids, etc. My invention is, however, particularly important in the manufacture of greases for use at more elevated temperatures from fatty acids made from hydrogenated fats. These fatty acids are very high in true stearic acid content and although the use of soaps made from these acids is highly desirable it has been found very difficult to produce the desired greases from them since it is necessary to use more elevated temperatures than in the case of oleic acid or mixed fatty acids. In the prior art procedure in which greases were made by the open kettle method from fatty acids split from hydrogenated fats, about one batch out of four was spoiled and even the remaining batches were of poor quality. The greases produced were often cloudy and the oil would tend to leak out of them.

As an example of the manufacture of greases according to my invention from fatty acids split from hydrogenated fats (in other words, from relatively pure stearic acid), I add the required amount of lime to a small amount of the previous batch of grease left in the kettle and I then add about 25% of the total required oil. After the old grease, lime and oil have been stirred up to a smooth consistency I add the fatty acids. If the oil is added after the fatty acids there is considerably more trouble from foaming.

Next I turn steam into the steam jacket surrounding the bottom of the kettle and when the batch has reached a smooth consistency and is up to about 150 F. to 175 F. temperature, I add the caustic soda solution. The batch will foam very little unless the operator tries to speed up by using side jacket steam in order to gain time. I try to keep down foaming as much as possible.

As in the preparation of cup greases, I circulate .-..the mix by means of a small pump beginning when the batch reaches 200 F. As stated before, this cuts down the tendency to foam and aids in keeping all constituents in a smooth even mix. I let the temperature of the batch get .up to 230* F. to 250 F. at which time the soap will be clear and stringy in appearance when hot and brittle when cold. Then I turn off the steam, bleed the jackets, start a small stream of water in the mixer and regulate the size of the stream by the amount of foaming. Circulation of the mixture through the pump is continued. If the mix starts to rise in the kettle the stream of water is cut off until it settles down.

As the mix cools down it will go through a characteristic change in appearance at about 220 F. to 225 F. Instead of a soapy appearance it will assume the typical appearance of a grease and will get much heavier. After this change has taken place a small stream of oil may be turned in to hasten the cooling. At or slightly above the boiling point of water the mix will be smooth in appearance and free from foam and tend to absorb more of the water instead of throwing it off as vapor, even though the mix is still above the boiling point of water. The proper moisture content can be fixed at this point before cooling the batch further.

After the addition of water is stopped, the remainder of the oil is added as rapidly as'it can be incorporated in the grease. The temperature of the oil should be about 130 F. to 150 F. The above procedure will finish up a batch of this type of grease in about to 5 hours with the temperature of the batch at the finish about 190 F. The steam pressure which I use is about 100 pounds per square inch and some variation in time'would result if steam at pressures other than that were used.

In operating according to my invention in the manufacture of greases from fatty acids split from hydrogenated fats, I find that the following advantages over prior art methods are obtained: the manipulation is much simpler and easier to carry out; I consistently obtain batches the properties of which check each othervery closely; samples taken for grease consistency on the day the batch is made give a true indication of the consistency of the product after some time in storage; it is possible to use more oil in proportion to the soap used and yet get the same consistency, thereby cutting down the cost .of my product without'sacriflcing quality; as the mixes are filled out and become cooler, the mass in the center of the larger containers does not lose moisture and separate or become crumbly, as sometimes happens with the old formed in a portion of the oil the procedure is much the same when using fatty acids split from hydrogenated fats as when using ordinary oleic acid or mixed fatty acids. The main differences are that when usingfatty acids made from hydrogenated fats the minimum soap making temperature is higher (230 F. to 250* F. as compared with 215 F. to 250 F.) and that the characteristic structural change also occurs at a higher temperature (220 F. to 225 F. instead of about 210 F.).

In either case, one of the most important features of my invention consists in slowly cooling the grease from a temperature within the range from about 215 F. to 250 F. to a critical temperature at which the characteristic structural change occurs (about 210 F. to 225 F. depending on the particular grease) while adding water and preferably oil very gradually and with especially thorough mixing. External mixing by removing grease from the bottom of the kettle and recirculating it to the top of the kettle is important if best results are to be obtained, as it provides exceptionally. good agitation and contact between the phases in a closed space out of contact with air which'would carry off water vapor rapidly at the temperature required.

The water content should be fixed at about the aforementioned critical temperature.' After this critical point is passed the remainder of the oil can be added rapidly and the grease is finished in the usual way.

The preceding description .has had particular reference to the manufacture of calcium soap greases from fatty acids. My invention is, however, also applicable to the manufacture of greases from fats. Thus, for instance, my invention can be applied to the manufacture of a lime-tallow grease in which the batch is heated to about 300 F. and held at this temperature during the saponification of the tallow.

While water must be present during the formation of a soap from fatty acid and lime, it is a necessary constituent in the reaction whereby a fat such as tallow (i. e. a glycerine fatty acid ester) is saponified:

By my method, where water is added continu- The saponification of tallow by this method takes but five hours where by the 01d method it required about 20 hours. The saving in time is due to my being able to hold the batch at a higher temperature (for instance 275 F. or higher). After the saponification of the tallow is completed, the procedure for making grease is the same as in the case of greases made from fatty acids as previously described.

Thus for instance a batch of transmission grease was made with lime and tallow in seven hours with as good a yield asI usually get when using free fatty acids and lime. Furthermore, the batch was made in about the same length of time (7 hours) as when it was made by the old method from fatty acids.

The advantages which my method has over the old method in making these lime-tallow greases, are the same as those previously cited for greases made from ordinary fatty acids. As stated-before, my method hastens the saponification by adding the water as fast as it is driven off and by insuring at all times a sufficient supply of water for the reaction. In the old method if sufficient water is added in'a batch at the start the high temperature cannot be obtained because of foaming. The new method makes it possible to use fats or fatty acids interchangeably which sometimes has economic advantages.

As previously stated my new method of grease manufactureutilizes the customary open kettle ,mixers exceptthat provision is made for external mixing by pumping a portion of the grease from the bottom of the kettle to the top.

The accompanying drawing which forms a open-topped kettle I0, is provided with a side steam jacket Ila and 'a bottom steam jacket lb, both of which may suitably be lagged. Steam is admitted through inlets I21: and I2?) and condensate is removed through valves |3a and l3b. These valves can also be used to bleed steam from the jacket when it is desired to cool the grease.

The kettle is provided with the .customary rotary mixers l4 carried by shaft l5 which is rotated by means of pulley I6 through gears l1. Elements 14, l5, l6 and I1 may suitably besupported by an I-beam .across the top of the kettle as shown.

Grease is withdrawn from the base of the kettle through valve l8 (operated by handle l9) pipe 20 and centrifugal pump 2| and is reintroduced into the top of the kettle through pipe 22.

Water and oil can be added along with the recirculated grease or may be introduced directly into the top of the. kettle. Thus oil may be added through pipe 23 and valve 24 which take suction from pump 2| or it may be added directly to the top of the kettle through valve 29. It is preferred not to add water directly in advance of pump 2| since this may result in vapor-locking the pump. Water is therefore added under the necessary pressure, through valve 25 or valve 26.

The finished grease may be removed directly from the bottom of the kettle or through valve 21 by means of pump 2| (after closing valves 24, 25 and 28) The various pipes, etc. may suitably be lagged or otherwise insulated or heated to prevent heat losses and clogging by cold grease.

To summarize my invention, all of my methods have as a necessary step the making of a soap in the presence of oil, the relative amount of the latter varying with the hardness of the soap desired, and adding water gradually to the soap mass so that the latter becomes a grease" oi a stable nature. In most cases this is carried out at temperatures in the vicinity of the boiling point of water, but in some cases, as for instance when fatty acids split from hydrogenated tats are used, it must be done well above the boiling point of water (e. g. 220 if). All methods require that the grease be cooled sufilciently to retain a part of the water. Vigorous mixing, preferably including external mixing by recycling material from the bottom of the kettle to the top, is also important. Also it the greases are reheated suiiiciently to drive 01! the water, the soap and oil will separate and the greases be ruined.

My new method makes all changes in the grease more gradual, yet accomplishes these changes in a shorter overall time due to my circulating the mix by means of a pump, and to mixing the constituents at higher temperatures than was possible under the old method and while the soap is still very heavy. The gradual changes in structure of the mix ensure that all of the soap will be used to its best advantage.

. This gives much greater yields 0! grease for a given amount of soap.

While I have described my invention in connection with certain specific embodiments thereof and together with certain theories to explain its advantages it is to be understood that these are by way of illustration rather than by way of limitation and I do not mean to be limited thereto but only to a liberal, valid interpretation oi ing the soap-oil mixture thus formed to a temperature within the range from about 230 F. to about 250 F., cooling the mixture'from a temperature within said range to a temperature at which said mixture changes from a soapy structure to a greasy structure, slowly and gradually adding water to said mixture throughout substantially the whole of said cooling, said change from a soapy structure to a greasy structure occurring at a temperature lower than said firstmentioned temperature and within the range from about 210 F. to about 225 F., and adding the remainder of the required lubricating oil, the addition of water and oil and being accompanied by constant mixing of the various materials involved.

2. A method for the manufacture of a calcium soap grease in an open grease kettle which comprises forming the calcium soap in a portion of the lubricating oil required in the grease, heating the soap-oil mixture thus iormed to a temperature within the range from about 230 F. to about 250 R, discontinuing heating at said temperature, slowly and gradually adding water and a small portion of the required lubricating oil while cooling the mixture from a temperature within said range to a temperature at which said mixture changes from a soapy structure to a greasy structure, said change occurring at a temperature lower than said first-mentioned temperature and within the range from about 210' F. to about 225 lubricating oil without further heating, the addition oi water and oil being accompanied by constant mixing oi the various materials involved.

3. A method for the manufacture of a calcium soap grease in an open mixing kettle which comprises forming the calcium soap in a portion of the lubricating oil required in the manufacture of said grease, heating the soap-oil mixture to a temperature above about 230 F., discontinuing heating at said temperature, adding water to said mixture slowly and gradually beginning at a temperature above about 230 F. while permitting said mixture to cool and while subjecting said mixture to thorough mixing, said mixing comprising externally circulating a portion of said mixture from the bottom of said kettle to the top of said kettle, continuing said cooling until a temperature is reached at which the mixture changes from a. characteristic soapy appearance to a characteristic greasy appearance, and then adding the remainder of the required lubricating oil while continuing the mixing operation.

4. A method for the manufacture of a calcium soap grease in an open kettle which comprises forming the calcium soap in at least about 15% of the total oil required in the final grease, mixing the oil and soap, heating the oil and soap mixture to a temperature of at least about 230 F., adding water to the mixture while permitting the mixture to cool ironna temperature of at least about 230' F. and while recycling a. portion of the mixture from the bottom of said kettle to the top of said kettle until a temperature within the range from about 210 F. to about 225 F. is reached, at which temperature the mixturechanges from a characteristic soapy appearance to a characteristic greasy appearance, discontinuing the addition of water at about the boiling point of water, further cooling the mixture, and adding the remainder ofthe oil required'in the final grease and incorporating said oil with the other constituents present.

5. In a method for the manufacture of a calcium soap grease in an open kettle, the steps which comprise subjecting a mixture of calcium soap and lubricating oil to a temperature of at least about 230 F., and then cooling said mixture while subjecting it to vigorous mixing and while gradually adding water beginning at a temperature of at least about 230 F. and ending when a temperature is reached at which the mass changes from a characteristic soapy appearance to a characteristic greasy appearance.

6. In the manufacture of a calcium soap grease in an open kettle the steps which comprise subjecting a mixture of calcium soap and lubricating oil to a temperature within the range from about 230 F. to about 250 F., slowly and gradually adding water and further lubricating oil beginning at said temperature while permitting the mixture to cool and while subjecting the mixture to further mixing, and discontinuing the addition of water at a temperature within the range from about 210 F. to about 225 F.

7. In the manufacture of a calcium soup grease in an open kettle the steps which comprise subjecting a mixture of calcium soap and lubricating oil to a temperature within the range from about 230 F. 'to about 250 F. slowly and gradually adding water and further lubricating oil beginning at said temperature while pormiitun: the mixture to cool, while subjecting the mixture in further mixing and while externally rirculuiin a portion of the mixture from the bottom of said kettle to the top of said kettle, and discontinuing aoaaous the addition of water at about the boiling point of water.

8. A method of manufacturing a calcium soap grease in a mixer of the open steam kettle type which comprises forming a calcium soap from lime and fatty acids in from about 15% to about 30% of the total lubricating oil required in said grease, heating the soap oil mixture to a temperature of from about 230 F. to about 250 F., cooling said mixture while subjecting it .to further mixing and while externally circulating a portion of said mixture from the bottom of said kettle to the top of said kettle, slowly and gradually adding water substantially throughout said cooling until a temperature within the range from about 210 F. to about 225 F. is reached, discontinuing the addition of water at about the boiling point of water, and further cooling the mixture while adding and incorporating the remainder of the required lubricating oil.

9. A method for the manufacture of a calcium soap grease in an open kettle whichcomprises forming soap from lime, a small amount of soda, and fatty acids split from hydrogenated fats in a portion of the lubricating oil required in the grease, mixing the soap and oil, heating the mixture to a temperature within the range from about 230 F. to about 250 F., gradually adding water and oil beginning at said temperature while cooling the mixture and while subjecting the mixture to further mixing, and completing the addition of the required water at a temperature of about 210 F.

10. A method for the manufacture of a calcium soap grease in an open kettle which comprises forming soap from lime, a small amount of soda and fatty acids split from hydrogenated fats in a portion of the lubricating oil required in the grease, mixing the soap and oil, heating the mixture to a temperature within the range from about 230 F. to about 250? F., gradually a adding water and oil beginning at said temperature while cooling the mixture and while ex-- ternally circulating a portion of said mixture from the bottom of said kettle to the top of said kettle, and completing the addition ofv the required water at a temperature of about 210 F.

11. A process for the manufacture of a calcium soap grease from lime and fat which comprises saponifying the fat with lime in the presence of a portion of the required lubricating oil while slowly and gradually adding water and while externally circulating a portion of the mixture from a point distant from the point at which said water is added to a point adjacent the point at which said water is added, completing the saponification, bringing the mixture thus formed to a temperature within the range from about 230 F. to about 250 F., slowly and gradually adding the additional water required to produce a grease structure while cooling the mixture from said temperature to a temperature at which the mixture changes from a characteristic soapy appearance to a characteristic greasy appearance.

12. Steps according to claim 5 in which said vigorous mixing comprises externally circulating a portion of the mixture from the bottom of said kettle to the top of said kettle.

13. A process according to claim 11 in which the cooling and addition of water are accompanied by additional external circulation of a h pprtion of the mixture.

CHARLES O. GREENLEE. 

